This invention relates to gas compression systems, and more particularly to a closed oil gas compression system utilizing a liquid ring pump.
Many of the existing hydrocarbon formations have been produced to such a point that the natural gas available in these reserves is at low pressures or below atmospheric pressure. To produce natural gas from these reserves, the gas must be pumped from the formation and compressed for sale. The cost to pump and compress gas can be substantial; therefore, cost saving measures are important in making retrieval of the gas economically viable.
Generally a self contained compression system is used to extract natural gas from low or below pressure reserves, and is located on the well site. The compression system comprises a variety of apparatus, including a compressor. Typically, prior art compression systems employ a screw type compressor to draw gas from the formation and compress it for sale. However, screw compressors are expensive and require relatively high energy inputs to compress the gas. Further, these compressors have parts with metal-to-metal contact which require a constant oil source. The oil is deposited into the pump and eventually is carried away by the compressed gas, thus the screw pumps use oil and the oil source must regularly be replenished. Other compressor types commonly used in these applications also require a constant oil feed.
The gas extracted from some low or below pressure formations contain vapors and entrained liquid. Typical compression systems used with these wells must dry the gas before it can be compressed, because screw and other typical compressors cannot handle the liquid. In these systems, when the compressor encounters liquid or vapor the compressor will overload and shut down.
Therefore, there exists a need for a compression system which can handle gas having vapors and entrained liquid. Also, a closed oil system is desirable because the oil reserves need not be refilled as often. Finally, the compressor system should compress efficiently and at low cost.
The present invention is drawn to a closed oil compression system employing a liquid ring pump. The invention is an apparatus for compressing a gas from a well. The gas has entrained liquid and vapor. The apparatus has a scrubber vessel for receiving the gas and separating at least a portion of the liquid and vapor. A storage vessel stores a seal liquid. A liquid ring pump is connected to the scrubber vessel and storage vessel. Seal liquid is mixed with the gas before it enters the pump, and the liquid is used to compress the gas. A separator vessel is connected to the pump and the storage vessel for separating at least a portion of any seal liquid entrained in the gas and returning the separated seal liquid to the storage vessel.
The storage vessel is integral with the scrubber vessel. The scrubber has an internal partition which divides the scrubber vessel into a first and second chamber, wherein the second chamber is the storage vessel. The separator vessel has a coalescing filter that further separates seal liquid from the gas. The separator vessel has a cylindrical splash guard surrounding the coalescing filter. A scavenger line runs from the coalescing filter to a condition between the scrubber and the pump. The liquid ring pump is single stage having a single inlet and single outlet. Further the apparatus has a heat exchanger and temperature responsive valve. The temperature responsive valve routes seal liquid from the storage vessel through the heat exchanger before mixing with the gas if the temperature of the seal liquid is above a given temperature.
Further, the present invention encompasses a method of compressing wet gas from a well, the wet gas having entrained liquid and vapor. The method includes the steps of providing a suction scrubber, a storage vessel containing seal liquid, a liquid ring pump, and a discharge separator. At least a portion of the liquid and vapor are separated from the gas with the suction scrubber. The seal liquid is injected into the gas before it enters the liquid ring pump. The gas is compressed with the seal liquid in the liquid ring pump. At least a portion of any seal liquid from the gas is separated in the discharge separator and the separated liquid is fed back into the storage vessel.
Further steps include cooling the seal liquid before injection into the gas. A coalescing filter with a splash guard is provided in the discharge separator and the coalescing filter separates at least a portion of any seal liquid from the gas. A partition is provided in the suction scrubber to form the storage vessel.